[qemu-s390x] [PATCH v2 1/1] 390x/cpumodel: document S390FeatDef.bit not applicable

[Halil Pasic]

The 'bit' field of the 'S390FeatDef' structure is not applicable to all
its instances. Currently this field is not applicable, and remains
unused, iff the feature is of type S390_FEAT_TYPE_MISC. Having the value 0
specified for multiple such feature definition  was a little confusing,
as it's a perfectly legit bit value, and as the value of the bit
field is usually ought to be unique for each feature of a given
feature type.

Let us introduce a specialized macro for defining features of type
S390_FEAT_TYPE_MISC so, that one does not have to specify neither bit nor
type (as the later is implied).

Signed-off-by: Halil Pasic <address@hidden>
---

v1 -> v2
* Specialized feature initializer macro for type MISC that does not
  require a bit value instead of defining a 'not a bit number' (that
  is extremal) bit number.
---
 target/s390x/cpu_features.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/target/s390x/cpu_features.c b/target/s390x/cpu_features.c
index a5619f2893..3b9e2745e9 100644
--- a/target/s390x/cpu_features.c
+++ b/target/s390x/cpu_features.c
@@ -23,6 +23,10 @@
         .desc = _desc,                               \
     }
 
+/* S390FeatDef.bit is not applicable as there is no feature block. */
+#define FEAT_INIT_MISC(_name, _desc)                 \
+            FEAT_INIT(_name, S390_FEAT_TYPE_MISC, 0, _desc)
+
 /* indexed by feature number for easy lookup */
 static const S390FeatDef s390_features[] = {
     FEAT_INIT("esan3", S390_FEAT_TYPE_STFL, 0, "Instructions marked as n3"),
@@ -123,8 +127,8 @@ static const S390FeatDef s390_features[] = {
     FEAT_INIT("ib", S390_FEAT_TYPE_SCLP_CPU, 42, "SIE: Intervention bypass 
facility"),
     FEAT_INIT("cei", S390_FEAT_TYPE_SCLP_CPU, 43, "SIE: 
Conditional-external-interception facility"),
 
-    FEAT_INIT("dateh2", S390_FEAT_TYPE_MISC, 0, "DAT-enhancement facility 2"),
-    FEAT_INIT("cmm", S390_FEAT_TYPE_MISC, 0, "Collaborative-memory-management 
facility"),
+    FEAT_INIT_MISC("dateh2", "DAT-enhancement facility 2"),
+    FEAT_INIT_MISC("cmm", "Collaborative-memory-management facility"),
 
     FEAT_INIT("plo-cl", S390_FEAT_TYPE_PLO, 0, "PLO Compare and load (32 bit 
in general registers)"),
     FEAT_INIT("plo-clg", S390_FEAT_TYPE_PLO, 1, "PLO Compare and load (64 bit 
in parameter list)"),
-- 
2.13.5